Aoki 2008 GRB 060206没有变化的中间路上吸收线

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Title:		No Evidence for Variability of Intervening Absorption Lines toward GRB 060206: Implications for the Mg II Incidence Problem
Authors:		Aoki, Kentaro; Totani, Tomonori; Hattori, Takashi; Ohta, Kouji; Kawabata, Koji S.; Kobayashi, Naoto; Iye, Masanori; Nomoto, Ken-ichi; Kawai, Nobuyuki
Publication:		eprint arXiv:0808.4157
Publication Date:		08/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Submitted tp PASJ
Bibliographic Code:		2008arXiv0808.4157A

Abstract

We examine variability of absorption line strength of intervening systems along the line of sight to GRB 060206 at z=4.05, by the low-resolution optical spectra obtained by the Subaru telescope from six to ten hours after the burst. Although strong variabilities of Fe II and Mg II lines at z=1.48 during t=5-8 hours have been reported for this GRB (Hao et al. 2007), our spectra with higher signal-to-noise ratio do not show any evidence for variability in t=6-10 hours. There is a clear discrepancy between our data and Hao et al. data in the overlapping time interval. Furthermore, the line strengths in our data are in good agreement with those observed at t~2 hours by Thone et al.(2008). We also detected Fe II and Mg II absorption lines for a system at z=2.26, and these lines do not show evidence for variability either. Therefore we conclude that there is no evidence for variability of intervening absorption lines toward GRB 060206. The intervening line variability has been used to support the idea of clumpy Mg II cloudlets that was originally proposed to explain the anomalously high incidence of Mg II absorbers in GRB spectra compared with quasars, but this Mg II incidence anomaly should be explained by other effects.

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Liu 2008 GRB 060206的进动模型

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后期光学增亮来自于另一个方向的喷流

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arXiv:0808.1172 [ps, pdf, other]

Title: GRB 060206: hints of precession of the central engine?

Authors: X.W. Liu, X.F. Wu, T. Lu

Comments: 6 pages, 2 figures

Journal-ref: 2008A&A...487..503

Subjects: Astrophysics (astro-ph)

Aims. The high-redshift (z = 4:048) gamma-ray burst GRB 060206 showed unusual behavior, with a significant rebrightening by a factor of ~ 4 at about 3000 s after the burst. We argue that this rebrightening implies that the central engine became active again after the main burst produced by the first ejecta, then drove another more collimated jet-like ejecta with a larger viewing angle. The two ejecta both interacted with the ambient medium, giving rise to forward shocks that propagated into the ambient medium and reverse shocks that penetrated into the ejecta. The total emission was a combination of the emissions from the reverse- and forward- shocked regions. We discuss how this combined emission accounts for the observed rebrightening. Methods. We apply numerical models to calculate the light curves from the shocked regions, which include a forward shock originating in the first ejecta and a forward-reverse shock for the second ejecta. Results. We find evidence that the central engine became active again 2000 s after the main burst. The combined emission produced by interactions of these two ejecta with the ambient medium can describe the properties of the afterglow of this burst. We argue that the rapid rise in brightness at ~ 3000 s in the afterglow is due to the off-axis emission from the second ejecta. The precession of the torus or accretion disk of the central engine is a natural explanation for the departure of the second ejecta from the line of sight.

Dainotti 2007 GRB 060218 and binary model

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Observation summarized first, then pointed out that: collapse of NS in a binary system can give this low energetic thing.

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arXiv:0712.0567 [ps, pdf, other]

Title: GRB 060218 and the binaries as progenitors of GRB-SN systems

Authors: Maria Giovanna Dainotti, Maria Grazia Bernardini, Carlo Luciano Bianco, Letizia Caito, Roberto Guida, Remo Ruffini

Comments: 6 pages, 3 figures, in the Proceedings of the "4th Italian-Sino Workshop on Relativistic Astrophysics", held in Pescara, Italy, July 20-28, 2007, C.L. Bianco, S.-S. Xue, Editors

Journal-ref: AIP Conf.Proc. 966 (2007) 25-30

Subjects: Astrophysics (astro-ph)

(shortened) We study the Gamma-Ray Burst (GRB) 060218: a particularly close source at z=0.033 with an extremely long duration, namely T_{90} ~ 2000 s, related to SN 2006aj. [...] I present the fitting time consuming procedure. In order to show its sensitivity I also present two examples of fits with the same value of B and different value of E_{e^\pm}^{tot}. We fit the X- and \gamma-ray observations by Swift of GRB 060218 in the 0.1-150 keV energy band during the entire time of observations from 0 all the way to 10^6 s within a unified theoretical model. The free parameters of our theory are only three, namely the total energy E_{e\pm}^{tot} of the e^\pm plasma, its baryon loading B \equiv M_Bc^2/E_{e\pm}^{tot}, as well as the CircumBurst Medium (CBM) distribution. We justify the extremely long duration of this GRB by a total energy E_{e\pm}^{tot} = 2.32\times 10^{50} erg, a very high value of the baryon loading B=1.0\times 10^{-2} and the effective CircumBurst Medium (CBM) density which shows a radial dependence n_{cbm} \propto r^{-\alpha} with 1.0 \leq \alpha \leq 1.7 and monotonically decreases from 1 to $10^{-6}$ particles/cm$^3$. We recall that this value of the $B$ parameter is the highest among the sources we have analyzed and it is very close to its absolute upper limit expected. [...] We also think that the smallest possible black hole, formed by the gravitational collapse of a neutron star in a binary system, is consistent with the especially low energetics of the class of GRBs associated with SNe Ib/c.

Curran 2007 Swift余辉的多波段同时拐折

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Swift之前大部分是同时拐折的，但Swift的暴却好像不是。作者通过对GRB 060206多波段余辉（X射线和光学）分析，发现还是同时拐折的，这样也比较符合标准激波模型。

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arXiv:0706.1188 [ps, pdf, other] :

Title: GRB 060206 and the quandary of achromatic breaks in afterglow light curves
Authors: P.A. Curran, A.J. van der Horst, R.A.M.J. Wijers, R.L.C. Starling, A.J. Castro-Tirado, J.P.U. Fynbo, J. Gorosabel, A.S. Jarvinen, D. Malesani, E. Rol, N.R. Tanvir, K. Wiersema, M.R. Burleigh, S.L. Casewell, P.D. Dobbie, S. Guziy, P. Jakobsson, M. Jelinek, P. Laursen, A.J. Levan, C.G. Mundell, J. Naranen, S. Piranomonte
Comments: 5 pages including 1 figure; submitted for publication in MNRAS Letters

Gamma-ray burst afterglow observations in the Swift era have a perceived lack of achromatic jet breaks compared to the BeppoSAX era. We examine the effect of the fact that pre-Swift afterglow observations tend to be dominated by the optical, whereas in the Swift era most well sampled light curves are in the X-ray. We present our multi-wavelength analysis of GRB 060206 as an illustrative example to demonstrate the possible effect of this change. The results of temporal and spectral analyses are compared, and attempts are made to fit the data within the context of the standard blast wave model. We find that while the break appears more pronounced in the optical and evidence for it from the X-ray alone is weak, the data are actually consistent with an achromatic break at about 16 hours. This break and the light curves fit standard blast wave models, either as a jet break or as an injection break. The Swift and pre-Swift samples of afterglows could well be consistent in their break behaviour, but the lack of accurate models for jet breaks and the dearth of well sampled late time optical light curves for Swift bursts preclude definitive statements on the matter.

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Hao 2006 GRB060206的铁镁吸收线

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astro-ph/0612409 [abs, ps, pdf, other] :

Title: Strongly Variable z=1.48 MgII and FeII Absorption in the Spectra of z=4.05 GRB 060206
Authors: H. Hao, K. Z. Stanek, A. Dobrzycki, T. Matheson, M. C. Bentz, J. Kuraszkiewicz, P. M. Garnavich, J. C. Howk, M. L. Calkins, G. Worthey, M. Modjaz, J. Serven
Comments: 14 pages, 4 figures, 1 table; ApJ Letters, submitted

We report on the discovery of strongly variable MgII and FeII absorption lines seen at z=1.48 in the spectra of the z=4.05 GRB 060206 obtained between 4.13 to 7.63 hours after the burst. In particular, the FeII line equivalent width (EW) decayed rapidly from 1.72+-0.25 AA to 0.28+-0.21 AA, only to increase to 0.96+-0.21 AA in a later date spectrum. The MgII doublet shows even more complicated evolution: the weaker line of the doublet drops from 2.05+-0.25 AA to 0.92+-0.32 AA, but then more than doubles to 2.47+-0.41 AA in later data. The ratio of the EWs for the MgII doublet is also variable, being closer to 1:1 (saturated regime) when the lines are stronger and becoming closer to 2:1 (unsaturated regime) when the lines are weaker, consistent with expectations based on atomic physics. We have investigated and rejected the possibility of any instrumental or atmospheric effects causing the observed strong variations. The possibility of variable intervening absorption in GRB spectra was recently predicted by Frank et al. (astro-ph/0605676). Our discovery of clearly variable intervening FeII and MgII lines lends very strong support to their scenario, in which the characteristic size of intervening patches of MgII ``clouds'' is comparable to the GRB beam size, i.e, about 10^16 cm. We discuss various implications of this discovery, including the nature of the MgII absorbers, the physics of GRBs, and measurements of chemical abundances from GRB and quasar absorption lines.